US2012/0255721 discloses an outdoor display apparatus which has an improved configuration to effectively prevent deterioration of a panel included therein. The outdoor display apparatus includes: a casing body having an air inlet and an air outlet, first and second display panel modules in the casing body to display images on front and rear surfaces of the casing body, respectively, transparent members fitted respectively to the front surface and the rear surface of the casing body to protect the first and second display panel modules, an air suction unit which comprises a fan to suction the air into the casing body through the inlet via an air filter and to discharge the air through the outlet, and an air distribution unit to distribute the air discharged from the air suction unit to at least one of the first display module and the second display module.
Such an outdoor display apparatus requires regular maintenance because the air filters have to be cleaned or replaced and the inside transparent members have to be cleaned occasionally. The maintenance of an outdoor display apparatus is very costly. The air space between the transparent member and the display panel causes poor visibility from light reflection and possible contamination by foreign particles and will reduced the view angle. Further, the fans will consume electrical power and generate noise. The apparatus will face internal moisture condensation if the ambient temperature is around zero degrees Celsius and even frost damage to the display panel glass layers especially if the apparatus is not powered at night to save electricity. The apparatus requires continuous operation or even heating and thus will have a high power consumption. In public places the transparent members are vulnerable to vandalism, this potential damage risk maybe reduced by increasing the thickness and laminating the transparent members, the glass will be costly, heavy and will significantly attenuate the light output of the display device so decreases the visibility in daytime. The whole construction is quite bulky.